The problem in particular is that carbon monoxide (CO) is an odorless, colorless, lethal gas when present in an environment, such as from incomplete combustion in automobiles, airplanes, recreational vehicle heater systems or home furnaces. Carbon monoxide's particular danger is that its presence is nondetectable by the five senses. It has no scent or color and it prevails unknowingly in the atmosphere as a lethal hazard to individuals. Many deaths result from lack of knowledge that this gas is present. Other gasses may be noxious but usually they have odors. They do not have the capability of depriving persons of oxygen in the bloodstream to their brain as does carbon monoxide.
A low level concentration of carbon monoxide to an individual in an environment over a prolonged period can be hazardous as well as a high level concentration over a short period. The hemoglobin has an affinity to pick up carbon monoxide at an estimated rate 250 times greater than that for oxygen. Discomfort can be experienced with long term exposure to carbon monoxide at as low as 35 parts per million (ppm) of atmoshpere. Symptoms of CO poisoning are headaches, nausea, dizziness, irritability, impaired reaction time and confusion. Continuous exposure to high concentrations will lead to convulsions, coma and death.
In this respect when the concentration level is at 200 ppm or above for a period of 2 to 3 hours the hemoglobin level may be in the order of 10% to 20% and a slight headache might be experienced to an individual in the environment. At 400 ppm for a period of 1 to 2 hours a severe headache can be expected and the hemoglobin level will be in the order of 20% to 30%. At 800 ppm for a 45 minute period convulsions can be expected and the hemoglobin level may be in the order of 30% to 40%. At 1600 ppm for a period of 45 minutes the hemoglobin level may be in the order of 50% to 60% and death might be expected.